During the next year we will pursue the following project: (1) Isolation and mapping of large chromosomal inversions generated spontaneously and generated by the transposon Tn10. (2) Fine structure mapping and complementation of point-deletion mutations affecting the transposon Tn5. We will attempt to identify determinants of the transposase and the transposition inhibitor. (3) Sequencing and characterization of an insertion sequence unique to Salmonella.